This invention relates to concrete batching and mixing plants in which quantities of materials are proportioned by weight and then mixed for use in making concrete structures. These plants are arranged to be set up in accessible locations and are designed for relatively small productive capacity.
It is an object of this invention to reduce the cost of such equipment and to simplify its function so that malfunction is unlikely to occur. The construction enables rapid production of concrete batches, flexibility as to mode of operation, and ease of control. Accuracy of control results in improved quality of concrete and consistency between batches.
In the mixing of concrete, it is customary in the batching plant to provide a silo for storing cement and suitable bins for various types of sand and other aggregates. One or more types of aggregates are selected for each type of concrete being furnished and the proportion of them in relation to the quantity of cement used determines the quality and other characteristics of the concrete product.
Generally the strength of the concrete is enhanced by reducing the quantity of water, but unless sufficient water is used, it is difficult to adequately mix the concrete and also to place it in various locations.
It has been proposed in the past to place the mixer on a scale (most commonly a load cell) and separately weigh the ingredients on the same scale as they are collected in the mixer or in hoppers integrally supported on the mixer so that a correctly proportioned batch of ingredients is assembled for mixing.
With these weighing arrangements, it was essential to weigh each ingredient separately. This required that each ingredient be fed separately into the weighing apparatus. Also that the apparatus be capable of having the feed interrupted when the desired weight of each material has been accumulated. Accordingly, there was no flexibility in the manner of introduction into the mixer of the cement and water vis-a-vis the aggregates. Should the water and cement be introduced first, stirring them together in the mixer can cause "balling", which is the creation of balls of cement and water. These balls are difficult to break up and cause a delay in production of a smooth, even mixture of concrete.
If each ingredient is introduced separately into the mixer, it is necessary to establish a sequence for such introduction since it is necessary to separately determine the quantity of each. This limits the flexibility of the plant.